1. Field of the Invention
The present invention concerns coffee, tea, cocoa, and other beverages containing milk constituents, and particularly concerns stabilized milk-constituent-containing beverages in which the germination of spores of and proliferation of heat-resistant spore-forming bacteria are inhibited and in which problems such as coagulation, oiling off, feathering, precipitation, neck ring, etc. of the milk constituents contained are suppressed.
The present invention applies to milk-constituent-containing beverages which are preserved and distributed in metal cans, such as aluminum cans, steel cans, etc., bottles, such as glass, ceramic, etc., and various other containers made of paper, synthetic resin, etc.
2. Description of the Prior Arts
Many beverages such as coffee, tea, cocoa, etc. contain milk constituents to improve flavor generally used, and taste, etc. The milk constituents used vary widely in type and amount, and include raw milk, raw cream, whole milk powder, skim milk powder, or instant creaming powder (ICP).
When stored over long periods of time, beverages containing milk constituents undergo loss of potable aptitude ( marketability) due to such problems as separation, oiling off, feathering, precipitation, neck ring, etc. of the milk constituents. Also, although milk-constituent-containing beverages are usually sterilized by retorting, there are cases where the spores of heat-resistant spore-forming bacteria survive under the conditions of such treatment. In cases where milk-constituent-containing beverages are sold or stored under low-temperature storage conditions in a vending machine, etc., there is little possibility of germination of spores of and proliferation of the surviving heat-resistant spore-forming bacteria and quality problems do not occur. However, if such beverages are placed in a heated condition, for example at 55.degree. C., the surviving spores of heat-resistant spore-forming bacteria can germinate and proliferate to cause the beverage contents to deteriorate and the beverage to thus lose potable aptitude ( marketability).
The combined use of a polyglycerin monoesters of fatty acids, comprising lauric acid and myristic acid, and mono-and diglycerides of fatty acids (laid-open Japanese patent publication No. Hei6-121640), the combined use of sucrose esters of fatty acids and citric acid esters of mono-and diglycerides of fatty acids (laid-open Japanese patent publication No. Hei5-15349), etc. have been proposed as methods of preventing deterioration and putrefaction of the beverage contents through prevention of germination of spores of and proliferation heat-resistant spore-forming bacteria and preventing undesirable effects due to physicochemical changes at the same time. However, with the former of the above methods, not only does the lauric acid, which is a lower fatty acid, damage the flavor significantly but the antibacterial effects are also inadequate. With the latter method, since sucrose esters of fatty acids is used, the effects of preventing the germination of spores of and proliferation of heat-resistant spore-forming bacteria are inadequate and unsatisfactory.
The present inventors have previously proposed the milk-constituent-containing beverage disclosed in Japanese patent application No. Hei7-144075 (laid-open Japanese patent application No. Hei8-228676). This prior art discloses a milk-constituent-containing beverage that uses diglycerol monoesters of fatty acids as emulsifier and is characterized in that 70wt. % or more of the fatty acid composition of the diglycerol monoesters of fatty acids is taken up by the total amount of myristic acid and/or palmitic acid. With this prior art, the germination of spores of and proliferation of heat-resistant spore-forming bacteria can be suppressed even when the beverage is stored at a high temperature over long periods.